In summary, we have studied the electromagnetic and gravitational radiation coming out of the system of a white dwarf orbiting a black hole. As a model of a white dwarf star we consider a zero temperature Bose-Fermi droplet of attractively interacting degenerate atomic bosons and spin-polarized atomic fermions. Our quantum hydrodynamics based simulations indeed show that the black hole-white dwarf binary system emits the electromagnetic energy in bursts, while crossing the periastron area. Such regular high energy blasts resemble ultraluminous X-ray bursts uncovered recently [1]}. Our simulations show that binary systems with heavier black holes radiate mostly in a quadrupole mode. On the other hand, the accretion disc emits energy mainly via dipole-type radiation, provided stellar- and intermediate-mass black holes are considered. This property can be used to determine the orientation of an orbital plane of a black hole-white dwarf binary system with respect to the observer on the Earth. Our simulations also show that at periastron the gravitational energy is emitted mainly at the very low frequencies. Moreover, they demonstrate that the binary system becomes a source of continues gravitational radiation as soon as the accretion disc is formed.
